Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Path: utzoo!mnetor!uunet!husc6!cmcl2!brl-adm!adm!vis!greg@bass.nosc.MIL
From: greg@bass.nosc.MIL
Newsgroups: comp.lang.c
Subject: Re: MAJOR ANSI C FLAW (my opinion, of course)
Message-ID: <9840@brl-adm.ARPA>
Date: Sun, 18-Oct-87 14:03:21 EDT
Article-I.D.: brl-adm.9840
Posted: Sun Oct 18 14:03:21 1987
Date-Received: Mon, 19-Oct-87 00:16:25 EDT
Sender: news@brl-adm.ARPA
Lines: 59

I think that this issue is important enough to add another message.
There is a way to allow full external name significance without
running afoul of old linkers, etc.

A source to source translator can be provided which reduces the
significance of C external identifiers to six monocase characters.
The design of such a tool is sketched below.  Given such a translator
available in the public domain, the ANSI Standard can require that
implementors either provide full significance throughout their
environment or provide such a translator.  The standard can also
strongly recommend the former as a quality issue.

I was willing to simply accept the restricted external namespace until
the recent message (I forget the author, sorry) explaining what this
will do to the interfaces to large packages, e.g., graphics and
database packages.  Such packages are becomming more and more common
in C programming environments.  This point woke me up to the severe
impact a restricted external namespace will have on the quality of our
programs.  Even a slight increase in maintenance difficulties becomes
a major expense and trial.

As I recall, a software tool to reduce name significance has already
been posted to net.sources.  It probably uses Unix tools, and anyway
it affects internal identifiers too, so its not suitable.  Here's what
I envision:

The tranlator would begin by reading a table of external identifiers
already seen and name substitutions already determined (in processing
other modules or entered by hand when C source isn't available for a
module) and then it would translate one or more modules.  New external
identifiers clashing with those previously seen would be given a
unique prefix, so that their full spelling is still available as a
comment and for those tools that can access it.  After translating the
modules, the augmented identifier table would be output.  Programmers
using debuggers, etc. can refer to the identifier table as needed.

I do not think such a translator need know much about C syntax.  Its
mostly a matter of ignoring reserved words and noticing whether an
identifier is mentioned outside of curly braces.  A fancier
implementation would avoid renaming typedefs, etc., but there would be
no harm in translating all externally mentioned symbols (other than
reserved words).  I also think that such a tool can be quite fast, not
greatly increasing compilation overhead.

If you're interested in writing such a tool, please send me a note.
I won't be able to take that on for a few weeks, and I think the
sooner such a tool is available the better.  Remember, it must be
public domain and be fully portable.


_Greg


J. Greg Davidson			  Virtual Infinity Systems
+1 (619) 452-8059        6231 Branting St; San Diego, CA 92122 USA
 
greg@vis.uucp				ucbvax--| telesoft--|
greg%vis.uucp@nosc.mil			decvax--+--sdcsvax--+--vis
greg%vis.uucp@sdcsvax.ucsd.edu		 ihnp4--|     nosc--|